Hypothermia in surgical patients has been shown to significantly increase the risk of surgical site infection and is associated with an increase in post-operative recovery time.
More than 40 million in-patient surgical procedures are performed annually in the United States. During each surgical procedure, each member of the surgical team wears a gown to prevent the transmission of infection from the health care worker to the patient, and each patient is draped with a drape that defines a sterile field that minimizes the transfer of microorganisms between non-sterile areas and the surgical wound.
In general, the patient is minimally clothed, and the operating room is maintained at a temperature of about 68° F. The operating room is maintained at a cool temperature to prevent the healthcare workers from overheating, or becoming uncomfortably warm during the procedure. In practice, the Association of Operating Room Nurses (AORN) and the Center for Disease Control and Prevention (CDC) support the American Institute of Architects Academy of Architecture recommendation that operating room temperatures be maintained between 68° F. and 73° F. However, operating room temperatures are often maintained at less than 68° F. due to surgeon preference, especially in cases where orthopedic surgeons, for example, wear added layers of protective clothing.
Nearly every surgical procedure employs some form of anesthesia. Studies have shown that anesthesia impairs the body's thermal regulatory process. In this regard, the core body temperature of a patient (i.e., the internal organ temperature) decreases a couple of degrees Celsius during surgery due simply to being anesthetized. In addition, most patients experience post anesthetic tremors (shivers). These shivers can break down body tissue, increase infection rates, and increase the time it takes for wounds to heal, all of which increase the time it takes the patient to recover from the surgical procedure. Moreover, the presence of anesthesia, in addition to impairing the thermal regulatory function of the patient, also constricts the blood vessels in the patient. This effect is termed vasoconstriction and is the body's attempt to insulate itself against further heat loss. Therefore, there is cyclical pattern of events during a surgical procedure that places the patient at risk of hypothermia: the use of anesthesia drops the patient's core temperature and reduces the patient's thermal regulation ability, and the cold patient experiences a constriction of blood vessels that impairs the body's ability to warm up.
There are negative consequences for patients who experience hypothermia. The negative consequences include adverse myocardial events, impaired platelet function, coagulopathy, reduced medication metabolism, including reduced metabolism of anesthesia, shivering which can lead to damage of body tissue, impaired wound healing, and increased risk of surgical site infection.
One conventional approach to warming a patient post surgically includes wrapping the patient's body in warm cotton towels. For the above reasons, an anesthetized patient is physiologically impaired from efficiently warming up after surgery. Post surgically, the patient will typically regain heat (i.e., warm up) at a rate of about one degree Celsius per hour. Thus, an extended period of time is required to warm the patient, which puts the patient at risk to surgical site infection and, at a minimum, increases post operative recovery time.
Certain conventional patient drapes provide a warm air flow over a patient during surgery. These conventional “warming drapes” blow heated air over the patient during surgery, and optionally, postoperatively. However, for the reasons described above, the anesthetized patient experiences a constriction of blood vessels that limits the effectiveness of convectively warming the patient. In addition, the forced flow of warm air has been associated with the undesired movement of debris onto the sterile field.
For these and other reasons, there is a need for the present invention.